1. Field of the Invention
The present invention relates to a gusseted tubing former designed to be incorporated in a manufacturing line, in particular for the manufacture of paper bags intended for the packaging industry. The former of the invention is also capable of being used in connection with other materials as well.
2. Description of Background and Other Information
A gusseted bag manufacturing line uses as raw material a continuous paper web in the form of a roll. During the processing of the web along the manufacturing line, various operations are performed, such as forming a tubing therealong, prior to the formation of individual paper bags. Along the manufacturing line, prior to the formation of the tubing at the former, the web is coated with glue on one of its sides. Thereafter, as the flat web is continuously moved along the manufacturing line, it is transformed into a continuous tube at the former as the two sides of the web rolled together and are attached by means of the glue.
The manufacturing process becomes more complicated when, in addition to the formation of a continuous web, lateral gussets, or folds, are to be formed. For this purpose, it is known to use a machine that manufactures paper bags from a continuous web, wherein the gussets are formed by means of a vacuum former around which the tubing is formed. The profile of the tubing is modified progressively by means of outside knurls that ensure the formation of the folds required for the formation of the gussets.
The profile of the former in the aforementioned machine is approximately triangular at the inlet, i.e., at the upstream end of the former, and it progressively flattens at the outlet, i.e., at the downstream end of the former, in a rectangular form.
The use of a vacuum former constitutes a major advance compared to prior techniques, particularly considering that it permits a continuous forming operation, which is a critical point in the manufacturing line. The manufacturing rate can be restricted by the ability of the former, including the aforementioned knurls, to allow for the folding of the tubing without tearing the tubing.
In current installations, the edges of the former are strictly linear and, therefore, fail to correspond, in any event, to the path followed by the paper web. Consequently, during the formation of the bags, the paper web is made to slide transversely over the former, particularly at the edges of the former. These are precisely the locations at which the frictional forces affecting the web are the greatest. Further, these forces frequently cause the web to tear when production rates are high.
These devices are extremely expensive for manufacturers since, in addition to the replacement of the paper web which is wasted upon tearing, it is necessary to restart the entire line, which necessitates the restarting of each work station, which consumes a very long period of time.